Takano Hideaki, Asano Katsuaki, Beppu Teruhiko, Ueda Kenji
Life Science Research Center, College of Bioresource Sciences, Nihon University, 1866 Kameino, Fujisawa 252-8510, Japan.
Gene. 2007 May 15;393(1-2):43-52. doi: 10.1016/j.gene.2007.01.026. Epub 2007 Feb 12.
Streptomyces griseus possesses multiple stress-response sigma factors including sigma(H). Previously, we have suggested that sigma(H) and related sigma factors are involved in the developmental control of S. griseus. Herein, we studied the role of two sigma(H) paralogs--sigma(F) and sigma(N)--which are encoded in tandem coding sequences of sigF-sigN in S. griseus [sigma(N) has been described as sigma(L) previously (Gene 320:127, 2003)]. A sigF mutant produced decreased levels of intracellular melanin and formed irregular spores. A triple mutant for sigHNF exhibited defective melanin production. While sigN was transcribed by three tandem promoters during the early to late growth phases, sigF was transcribed in the late developmental phase by a single promoter. The activity of the promoter preceding the rpp operon (Prpp), which is responsible for the intracellular melanin biosynthesis, was decreased in the sigF mutant and abolished in the sigHNF, adpA and A-factor biosynthesis mutants. The in vitro transcription assay demonstrated that Esigma(F) transcribed the rpp promoter. Both Esigma(F) and Esigma(N) transcribed a sigma(H)-dependent promoter that preceded the sigH operon, and their activities were repressed by the addition of RshA, an anti-sigma(H) protein. Overall, the results suggest that the three sigma factors have similar functions and that they are required for spore development and pigmentation. The transcription of the rpp operon is regulated both by the stress-response sigma factors and the A-factor regulatory cascade.
灰色链霉菌拥有多种应激反应西格玛因子，包括西格玛（H）。此前，我们曾提出西格玛（H）及相关西格玛因子参与灰色链霉菌的发育调控。在此，我们研究了两个西格玛（H）旁系同源物——西格玛（F）和西格玛（N）——它们由灰色链霉菌中sigF - sigN的串联编码序列编码[西格玛（N）先前被描述为西格玛（L）（《基因》320:127，2003年）]。一个sigF突变体产生的细胞内黑色素水平降低，形成不规则孢子。sigHNF的三重突变体表现出黑色素生成缺陷。虽然西格玛（N）在生长早期到晚期由三个串联启动子转录，但西格玛（F）在发育后期由单个启动子转录。负责细胞内黑色素生物合成的rpp操纵子之前的启动子（Prpp）的活性在sigF突变体中降低，在sigHNF、adpA和A因子生物合成突变体中消失。体外转录分析表明，E西格玛（F）转录rpp启动子。E西格玛（F）和E西格玛（N）都转录sigH操纵子之前的一个西格玛（H）依赖性启动子，并且添加抗西格玛（H）蛋白RshA会抑制它们的活性。总体而言，结果表明这三个西格玛因子具有相似功能，并且它们是孢子发育和色素沉着所必需的。rpp操纵子的转录受应激反应西格玛因子和A因子调控级联的调节。
